Abstract Geogenic arsenic (As) adversely affects drinking water quality in geologically diverse aquifers across the globe. Although the species of As significantly affects its fate, transport, toxicity, and As treatment technology efficacy, reported effectiveness of As species preservation methods varies widely with preservation methods and natural water geochemistry. Our study 1) evaluates the shelf life of As(III), As(V), dimethylarsinate (DMA), and monomethylarsonate (MMA) in standards prepared with ultrapure water; 2) establishes a hold time for these As species in low-iron (Fe) groundwater and surface water samples preserved with a concentration of EDTA that exceeded the sum of the molar concentrations of Al, Fe, Mn, Ca, Mg, and Sr (molar excess of EDTA); and 3) evaluates As(III) species stability in groundwater samples with detectable SO4 and up to 6.5 mg/L Fe concentrations preserved in 3 ways: less than molar excess EDTA, molar excess EDTA, and Vacuette® tubes with an unknown (proprietary) amount of EDTA. Arsenic species standards prepared with 2.5 mM EDTA in ultrapure water and stored at 4 °C had a shelf life of at least 180 days. As(III) was stable for at least 15 days and DMA and MMA were stable for at least 90 days in environmental samples with Fe less than 1 mg/L that were preserved with a molar excess of EDTA and stored in opaque containers at 4 °C. As(III) species were not stable for any holding time in samples with Fe greater than 1 mg/L and detectable SO4 when preserved with a molar excess of EDTA and stored in white high density polyethylene bottles at room temperature, or when preserved by storage in EDTA containing Vacuette® tubes at 4 °C. For geochemical or water quality studies where the distribution of As(III) and As(V) is a critical factor, an understanding of the sample chemistry, rapid As speciation analysis after sample collection, and collecting a field spike with the sample can be helpful for collecting accurate inorganic As species data.

中文翻译：

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三种不同保存方式下实验室标准、地表水和地下水中无机和甲基化砷物种的稳定性

摘要 地质成因砷 (As) 对全球地质多样的含水层中的饮用水质量产生不利影响。尽管 As 的种类对其命运、运输、毒性和 As 处理技术的功效有显着影响，但所报道的 As 种类保存方法的有效性因保存方法和天然水地球化学而有很大差异。我们的研究 1) 评估了用超纯水制备的标准品中 As(III)、As(V)、胂酸二甲酯 (DMA) 和胂酸甲酯 (MMA) 的保质期；2) 为低铁 (Fe) 地下水和地表水样品中的这些 As 物种建立保持时间，EDTA 浓度超过了 Al、Fe、Mn、Ca、Mg 和 Sr 的摩尔浓度总和（摩尔过量的 EDTA）；和 3) 评估地下水样品中 As(III) 物种的稳定性，其中可检测的 SO4 和高达 6.5 mg/L 的 Fe 浓度以 3 种方式保存：低于摩尔过量的 EDTA、摩尔过量的 EDTA 和具有未知（专有）的 Vacuette® 管EDTA 量。用 2.5 mM EDTA 在超纯水中制备并在 4 °C 下储存的砷物种标准品的保质期至少为 180 天。As(III) 在 Fe 小于 1 mg/L 的环境样品中至少稳定 15 天，DMA 和 MMA 稳定至少 90 天，这些样品用摩尔过量的 EDTA 保存并储存在不透明容器中 4° C。当用摩尔过量的 EDTA 保存并在室温下储存在白色高密度聚乙烯瓶中时，As(III) 物质在 Fe 大于 1 mg/L 和可检测到 SO4 的样品中的任何保持时间都不稳定，或在 4 °C 下保存在含有 Vacuette® 的 EDTA 管中。对于 As(III) 和 As(V) 的分布是关键因素的地球化学或水质研究，了解样品化学、样品采集后的快速 As 形态分析以及随样品采集现场尖峰可能会有所帮助用于收集准确的无机砷物种数据。